The Microbacteria

Abstract

A representative collection of species of the genus Microbacterium Orla-Jensen was studied. Morphologically, the organisms were found to be of 3 distinct types; viz., short, thin rods characteristic of M. lacticum; rod-shaped cells 0.7-0.9 X 1.4-2.6 [mu] characteristic of M. flavum; and blunt, wedge-shaped cells characteristic of Microbacterium sp. The above-mentioned group is biochemically well-differentiated. Microbacterium sp. fermented the greatest number of substrates tested, M. flavum the least. None of the cultures examined produced indole, H2S or liquefied gelatin. All of the organisms examined produced catalase and were able to form acid from glucose, fructose, mannose and galactose. Culturally, the organisms formed small "dewdrop" surface colonies 0.5-2 mm. in diam. on the usual agar media after 2-3 days at 30 C. The cultural characteristics are not sufficiently clear-cut to differentiate the 3 spp. of this property alone. A key for the identification of the 3 spp. is presented based upon the differential fermentation of raffinose, glycerol, starch and maltose.